Power conversion circuit with a compensation circuit

Abstract

In a power conversion circuit in which a grounded capacitor is connected to a main circuit that converts power through operation of a semiconductor switching device, a control IC that supplies a drive signal to the semiconductor switching device generates a cancellation voltage for canceling out a conducted emission that develops across terminals of the grounded capacitor as a result of the operation of the semiconductor switching device by using the drive signal (gate signal) to control a charge/discharge current of a compensation capacitor in a compensation circuit that is externally connected to the main circuit.

What is claimed is: 
     
       1. A power conversion circuit, comprising:
 a semiconductor switching device; 
 a main circuit that performs power conversion through switching on and off of the semiconductor switching device, the main circuit including a controller that supplies a drive signal to the semiconductor switching device to switch on and off the semiconductor switching device, 
 a grounded capacitor connected to the main circuit; 
 a compensation circuit separate from the main circuit, connected to the main circuit, the compensation circuit including a compensation capacitor; and 
 a compensation generator connected to the compensation circuit, the compensation generator charging and discharging the compensation capacitor on the basis of the drive signal so as to generate a cancellation voltage across the compensation capacitor that causes a conducted emission voltage across terminals of the grounded capacitor generated as a result of the switching on and off of the semiconductor switching device to be cancelled out, thereby eliminating conducted emission, 
 wherein the compensation generator is included within the main circuit or within the compensation circuit, and 
 wherein the compensation circuit further includes a delay time setter that adjusts timings at which the compensation capacitor is charged and discharged in accordance with delay times in ON and OFF switching of the semiconductor switching device relative to the drive signal. 
 
     
     
       2. The power conversion circuit according to  claim 1 , wherein the compensation generator is included within the controller of the main circuit, and the compensation generator includes a first current source for charging the compensation capacitor and a second current source for discharging the compensation capacitor that are alternately switched in accordance with the drive signal. 
     
     
       3. The power conversion circuit according to  claim 2 , wherein the controller is integrated with the first and second current sources into a single integrated circuit. 
     
     
       4. The power conversion circuit according to  claim 1 , wherein the delay time setter includes a series circuit made of a parallel circuit constituted by a diode and a resistor and a delay time setting capacitor that is connected in series to the parallel circuit, and the series circuit is connected between a ground voltage and the first and second current sources that are alternately switched in accordance with the drive signal. 
     
     
       5. The power conversion circuit according to  claim 1 , wherein a first series circuit constituted by a diode and a resistor is connected in series to the compensation capacitor for adjusting a leading edge slope of the cancellation voltage, and a second series circuit constituted by a diode and a resistor is connected in series to the compensation capacitor for adjusting a trailing edge slope of the cancellation voltage. 
     
     
       6. The power conversion circuit according to  claim 5 , wherein the first and second series circuits are included within the compensation circuit. 
     
     
       7. The power conversion circuit according to  claim 1 ,
 wherein the compensation generator is included within the controller of the main circuit, 
 wherein the compensation generator includes a first current source for charging the compensation capacitor and a second current source for discharging the compensation capacitor that are alternately switched in accordance with the drive signal, 
 wherein the delay time setter includes a series circuit made of a parallel circuit constituted by a diode and a resistor and a delay time setting capacitor that is connected in series to the parallel circuit, and the series circuit is connected between a ground voltage and the first and second current sources that are alternately switched in accordance with the drive signal, and 
 wherein the compensation circuit further includes a first series circuit constituted by a diode and a resistor connected in series to the compensation capacitor for adjusting a leading edge slope of the cancellation voltage, and a second series circuit constituted by a diode and a resistor connected in series to the compensation capacitor for adjusting a trailing edge slope of the cancellation voltage. 
 
     
     
       8. The power conversion circuit according to  claim 1 , wherein the compensation generator and the compensation circuit are configured to generate the cancellation voltage that has ON/OFF delay times, a leading edge slope and a trailing edge slope that respectively correspond to ON/OFF delay times, a leading edge slope and a trailing edge slope of the conducted emission voltage. 
     
     
       9. A power conversion circuit, comprising:
 a semiconductor switching device; 
 a main circuit that performs power conversion through switching on and off of the semiconductor switching device, the main circuit including a controller that supplies a drive signal to the semiconductor switching device for the switching on and off of the semiconductor switching device, 
 a grounded capacitor connected to the main circuit; 
 a compensation circuit separate from the main circuit, connected to the main circuit, the compensation circuit including a compensation capacitor; and 
 a compensation generator connected to the compensation circuit, the compensation generator charging and discharging the compensation capacitor, 
 wherein the compensation generator is included within the main circuit or within the compensation circuit, and 
 wherein the compensation circuit further includes a delay time setter that adjusts timings at which the compensation capacitor is charged and discharged in accordance with delay times in ON and Off switching of the semiconductor switching device relative to the drive signal. 
 
     
     
       10. The power conversion circuit according to  claim 9 ,
 wherein a compensation current caused by the compensation generator flows in the compensation capacitor in a first direction when the semiconductor switching device is being turned on so as to charge the compensation capacitor, and 
 wherein the compensation current flows in the compensation capacitor in a second direction that is opposite to the first direction when the semiconductor switching device is being turned off so as to discharge the compensation capacitor. 
 
     
     
       11. The power conversion circuit according to  claim 9 , wherein the compensation generator is included within the controller of the main circuit, and the compensation generator includes a first current source for charging the compensation capacitor and a second current source for discharging the compensation capacitor that are alternately switched in accordance with the drive signal. 
     
     
       12. The power conversion circuit according to  claim 11 , wherein the controller is integrated with the first and second current sources into a single integrated circuit. 
     
     
       13. The power conversion circuit according to  claim 10 , wherein the compensation generator charges and discharges the compensation capacitor by using the drive signal so as to generate a cancellation voltage for the compensation current across the compensation capacitor that causes a conducted emission voltage across terminals of the grounded capacitor generated as a result of the switching on and off of the semiconductor switching device to be cancelled out, thereby eliminating the conducted emission voltage. 
     
     
       14. The power conversion circuit according to  claim 9 , wherein the delay time setter includes a series circuit made of a parallel circuit constituted by a diode and a resistor and a delay time setting capacitor that is connected in series to the parallel circuit, and the series circuit is connected between a ground voltage and the first and second current sources that are alternately switched in accordance with the drive signal. 
     
     
       15. The power conversion circuit according to  claim 13 , wherein a first series circuit constituted by a diode and a resistor is connected in series to the compensation capacitor for adjusting a leading edge slope of the cancellation voltage, and a second series circuit constituted by a diode and a resistor is connected in series to the compensation capacitor for adjusting a trailing edge slope of the cancellation voltage. 
     
     
       16. The power conversion circuit according to  claim 15 , wherein the first and second series circuits are included within the compensation circuit. 
     
     
       17. The power conversion circuit according to  claim 13 ,
 wherein the compensation generator is included within the controller of the main circuit, 
 wherein the compensation generator includes a first current source for charging the compensation capacitor and a second current source for discharging the compensation capacitor that are alternately switched in accordance with the drive signal, 
 wherein the delay time setter includes a series circuit made of a parallel circuit constituted by a diode and a resistor and a delay time setting capacitor that is connected in series to the parallel circuit, and the series circuit is connected between a ground voltage and the first and second current sources that are alternately switched in accordance with the drive signal, and 
 wherein the compensation circuit further includes a first series circuit constituted by a diode and a resistor connected in series to the compensation capacitor for adjusting a leading edge slope of the cancellation voltage, and a second series circuit constituted by a diode and a resistor connected in series to the compensation capacitor for adjusting a trailing edge slope of the cancellation voltage. 
 
     
     
       18. The power conversion circuit according to  claim 13 , wherein the compensation generator and the compensation circuit are configured to generate the cancellation voltage that has ON/OFF delay times, a leading edge slope and a trailing edge slope that respectively correspond to ON/OFF delay times, a leading edge slope and a trailing edge slope of the conducted emission voltage. 
     
     
       19. The power conversion circuit according to  claim 10 ,
 wherein the main circuit includes a rectifier circuit having a pair of input terminals to receives an AC voltage input, and an inductor that receives an output of the rectifier, and 
 wherein:
 the semiconductor switching device receives an output of the inductor; and 
 the grounded capacitor is connected to one of the pair of input terminals, and 
 the compensation current flows through the compensation capacitor, the rectifier, and the grounded capacitor when the semiconductor switching device is turned on and off. 
 
 
     
     
       20. The power conversion circuit according to  claim 10 , wherein:
 the compensation generator and the compensation circuit are configured to generate a cancellation voltage for the compensation current, 
 the cancellation voltage has ON and OFF delay times, a leading edge slope and a trailing edge slope, 
 the ON delay time corresponds to a time difference between a rising edge of the drive signal and a time at which the semiconductor switching device starts being turned on, 
 the OFF delay time corresponds to a time difference between a falling edge of the drive signal and a time at which the semiconductor switching device starts being turned off, 
 the leading edge slope corresponds to changing from the switching off to the switching of the semiconductor switching device, and 
 the trailing edge slope corresponds to changing from the switching on to the switching off of the semiconductor switching device.